1. Field of the Invention
The present invention relates, generally, to methods of forming a guanidine group on carbon nanotubes (CNTs) and of attaching CNTs having guanidine groups to a substrate, and CNTs and a substrate manufactured by the above methods. More specifically, the present invention relates to a method of forming a guanidine group on CNTs to improve the dispersibility of CNTs, a method of attaching CNTs having guanidine groups to a substrate by combining the guanidine group with the crown ether, and CNTs and a substrate manufactured by the above methods.
2. Description of the Related Art
Dispersion of CNTs is essential for all pre-treatment processes using the CNTs. However, in cases where the CNTs are dispersed in water or a protic solvent, it is difficult to uniformly disperse the CNTs, composed completely of carbons, in the solvent. Therefore, a dispersing agent, such as a surfactant, is used. To achieve the uniform dispersion of the CNTs, the CNTs that are partially negatively charged should be formed in the shapes of micelles or inverse micelles including CNTs surrounded by the dispersing agent. As such, the dispersing agent is used in a predetermined concentration or more. In addition, various dispersing agents, such as nonionic-, cationic-, anionic-, and polymeric-type dispersing agents, are typically used. However, the dispersing agent surrounding the CNTs may function as an impurity in the process of using the CNTs.
Hence, since the dispersing agent used for the dispersion of the CNTs may cause problems in the subsequent process, methods of introducing a functional group able to directly react with the solvent to the CNTs have been proposed to uniformly disperse the CNTs while solving the above problems. For example, methods of forming a carboxyl group, a hydroxy group or an amine group on CNTs have been known.
In this regard, U.S. Pat. No. 6,368,569 discloses a method of forming a carboxyl group on CNTs, and U.S. Pat. Nos. 6,187,823 and 6,331,262 disclose a method of forming an amine group on CNTs. When the carboxyl group (—COOH) as a hydrophilic functional group is introduced to the CNTs, the CNTs are surrounded with water molecules due to the hydrogen bond between the carboxyl group and the water molecule of H—O—H. Thus, the CNTs are uniformly dispersed at regular intervals in water, even without the use of the dispersing agent. The amine group, which is a hydrophilic functional group, is hydrogen bonded with a water molecule so that the CNTs are dispersed in the solvent.
However, in the cases where a metal cation is present in the solution, the carboxyl group or amine group of the CNTs may be undesirably chelated with the metal cation.